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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
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    <title>Document</title>
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<body>
   <script>
    var obj = {
        o:'hello',
        "123":"world"
    }
    console.log(obj['123'])
    </script> 
</body>
</html>